Field of the Invention
The present invention relates to a method of selectively controlling the self-sealing ability of a tyre and to a self-sealing tyre for vehicle wheels.
Description of the Related Art
A tyre for vehicle wheels generally comprises a carcass structure associated with a belt structure. A tread band is applied at a radially external position to the belt structure. The green tyre is build through assembly of respective semi-finished products of an elastomeric blend.
After building of the green tyre carried out by assembly of respective components, a curing and molding treatment is generally carried out which aims at determining the structural stabilisation of the tyre through cross-linking of the elastomeric compositions and also at impressing it with a desired tread pattern and possible distinctive graphic marks at the sidewalls.
Self-sealing tyres are known that are able to delay or prevent the escape of air and the consequent tyre deflation due to a puncture caused by a sharp-pointed object (a nail, for example). In order to obtain this result, a self-sealing tyre comprises at least one layer of sealing polymeric material that can adhere to the object inserted therein and can further flow into the puncture or hole when this object is removed, thereby sealing the hole itself and preventing the escape of air from the tyre. This material inside the finished (cured and molded) tyre must be deformable and sticky.
Document EP 1 435 301 discloses a self-sealing tyre obtained by disposing an elastomeric composition, containing 0.2 to 20 parts by weight of a peroxide based on 100 parts by weight of an elastomer containing not less than 50% by weight of polyisobuthylene, at an inner surface of an uncured tyre. In an embodiment, a film of thermoplastic resin is disposed on a radially internal side of the sealing layer. The thickness of the thermoplastic-resin film is included between 0.05 mm and 0.3 mm. The elastomeric composition is heated during the tyre curing, causing a reaction involving decomposition of the polyisobutylene and formation of an elastomeric sealing layer.